French Rugby Federation president Bernard Laporte claims he is the victim of a coup after being taken into custody in Paris.
Laporte is being investigated for his links to the Altrad Group, owned by Montpellier owner Mohed Altrad.
Altrad himself was one of four other individuals also being questioned at the offices of the Brigade for the Repression of Economic Crime (BRDE).
The others are French Rugby Federation (FFR) vice-president Serge Simon, the FFR's international relations executive Nicolas Hourquet and Claude Atcher, the director general of the 2023 Rugby World Cup organising committee.
Their questioning comes just ten days before the FFR presidential elections, at which Laporte is seeking a second term.
However, the investigation dates back to 2017 when it's alleged he pressurised the French League's (LNR) appeals committee to drop sanctions against Montpellier for the display of critical banners at Montpellier's Altrad Stadium.
His intervention led to seven members of the committee to resign.
Later that year, Altrad were confirmed as the first ever shirt sponsors of the French national team, and added their financial heft to the country's World Cup bid.
Following his questioning, Laporte released an open letter to French clubs, saying, "With 10 days to go to a key deadline for our federation, an organised campaign of destabilisation is trying to take French rugby down.
"It's a true attempt at a coup of which there is no doubt about the motivation of the creators. It all adds up to a truly foul electoral strategy".
Laporte's lawyer Jean-Pierre Versini-Campinchi insisted his client is innocent of any crime, "He is perfectly calm about the questions that are likely to be put to him.
"But he is offended, he is angry that it is in the middle of the campaign ten days before the elections, that the public prosecutor of Paris felt that it was absolutely necessary to hear him.
"He is all the more serene as he does not see what he is being criticised for."